Method for fabricating semiconductor device with redistribution plugs

ABSTRACT

The present application discloses a method for fabricating a semiconductor device. The method includes providing a first chip comprising a first substrate, a first redistribution layer positioned above the first substrate, a first lower bonding pad positioned on the first redistribution layer, and a second lower bonding pad positioned above the first substrate and distant from the first lower bonding pad. The method also includes providing a second chip comprising a dense region and a loose region adjacent to the dense region; a plurality of upper pads positioned on the first lower bonding pad and the second lower bonding pad; and a plurality of second redistribution layers positioned on the plurality of upper pads. The method further performs bonding the second chip onto the first chip in a face-to-face manner, wherein the plurality of upper pads contact the first lower bonding pad and the second lower bonding pad.

TECHNICAL FIELD

The present disclosure relates to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a semiconductor device with redistribution plugs.

DISCUSSION OF THE BACKGROUND

Semiconductor devices are used in a variety of electronic applications, such as personal computers, cellular telephones, digital cameras, and other electronic equipment. The dimensions of semiconductor devices are continuously being scaled down to meet the increasing demand of computing ability. However, a variety of issues arise during the scaling-down process, and such issues are continuously increasing. Therefore, challenges remain in achieving improved quality, yield, performance, and reliability and reduced complexity.

This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this section constitutes prior art to the present disclosure, and no part of this Discussion of the Background section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure.

SUMMARY

One aspect of the present disclosure provides a semiconductor device including a first chip including a first substrate, a first redistribution layer positioned above the first substrate, a first lower bonding pad positioned on the first redistribution layer, and a second lower bonding pad positioned above the first substrate and distant from the first lower bonding pad; and a second chip including a dense region and a loose region adjacent to the dense region, a plurality of upper pads positioned on the first lower bonding pad and the second lower bonding pad, a plurality of second redistribution layers positioned on the plurality of upper pads, and a first redistribution plug and a second redistribution plug respectively and correspondingly positioned on the plurality of second redistribution layers. The first redistribution plug is at the dense region and includes a first aspect ratio. The second redistribution plug is at the loose region and includes a second aspect ratio less than the first aspect ratio.

Another aspect of the present disclosure provides a semiconductor device including a first chip including a first substrate, a first redistribution layer positioned above the first substrate, a first lower bonding pad positioned on the first redistribution layer, a second lower bonding pad positioned above the first substrate and distant from the first lower bonding pad, and a plug structure positioned between the second lower bonding pad and the first substrate; and a second chip including a dense region and a loose region adjacent to the dense region, a plurality of upper pads positioned on the first lower bonding pad and the second lower bonding pad, a plurality of second redistribution layers positioned on the plurality of upper pads, and a first redistribution plug and a second redistribution plug respectively and correspondingly positioned on the plurality of second redistribution layers. The first redistribution plug is at the dense region, electrically couples to the first redistribution layer, and includes a first aspect ratio. The second redistribution plug is at the loose region, electrically couples to the plug structure, and includes a second aspect ratio less than the first aspect ratio.

Another aspect of the present disclosure provides a method for fabricating a semiconductor device including providing a first chip including a first substrate, a first redistribution layer above the first substrate, a first lower bonding pad on the first redistribution layer, and a second lower bonding pad above the first substrate and distant from the first lower bonding pad; providing a second chip including a second substrate including a dense region and a loose region adjacent to the dense region, a plurality of storage units above the second substrate, a first redistribution plug above the dense region and a second redistribution plug above the loose region, a plurality of second redistribution layers on the first redistribution plug and the second redistribution plug, respectively and correspondingly, a plurality of upper pads on the plurality of second redistribution layers, respectively and correspondingly; and bonding the second chip onto the first chip in a face-to-face manner to contact the plurality of upper pads to the first lower bonding pad and the second lower bonding pad. The first redistribution plug includes a first aspect ratio, and the second redistribution plug includes a second aspect ratio less than the first aspect ratio.

Due to the design of the semiconductor device of the present disclosure, the first redistribution plug and the second redistribution plug having different aspect ratios may be used to fine tune resistances for different redistribution paths. As a result, the performance of the semiconductor device may be improved. In addition, data signals may be transmitted through the upper pads, the first lower bonding pad, and the first redistribution layer without passing through the conductive features, the plug structure, and functional units of the first chip. As a result, the distance of transmittance may be reduced so that the performance of the semiconductor device may be improved. Furthermore, the power consumption of the semiconductor device may be reduced due to the shorter distance of transmittance.

The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, and form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates, in a flowchart diagram form, a method for fabricating a semiconductor device in accordance with one embodiment of the present disclosure;

FIGS. 2 to 6 illustrate, in schematic cross-sectional view diagrams, part of a flow for fabricating the semiconductor device in accordance with one embodiment of the present disclosure;

FIG. 7 illustrates, in a schematic top-view diagram, an intermediate semiconductor device in accordance with one embodiment of the present disclosure;

FIG. 8 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 7 ;

FIG. 9 illustrates, in a schematic top-view diagram, an intermediate semiconductor device in accordance with one embodiment of the present disclosure;

FIG. 10 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 9 ;

FIG. 11 illustrates, in a schematic top-view diagram, an intermediate semiconductor device in accordance with one embodiment of the present disclosure;

FIG. 12 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 11 ;

FIG. 13 illustrates, in a schematic top-view diagram, an intermediate semiconductor device illustrated in accordance with one embodiment of the present disclosure;

FIG. 14 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 13 ;

FIG. 15 illustrates, in a schematic cross-sectional view diagram, part of the flow for fabricating the semiconductor device in accordance with one embodiment of the present disclosure;

FIGS. 16 to 21 illustrate, in schematic cross-sectional view diagrams, semiconductor devices in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

It should be understood that when an element or layer is referred to as being “connected to” or “coupled to” another element or layer, it can be directly connected to or coupled to another element or layer, or intervening elements or layers may be present.

It should be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. Unless indicated otherwise, these terms are only used to distinguish one element from another element. Thus, for example, a first element, a first component or a first section discussed below could be termed a second element, a second component or a second section without departing from the teachings of the present disclosure.

Unless the context indicates otherwise, terms such as “same,” “equal,” “planar,” or “coplanar,” as used herein when referring to orientation, layout, location, shapes, sizes, amounts, or other measures do not necessarily mean an exactly identical orientation, layout, location, shape, size, amount, or other measure, but are intended to encompass nearly identical orientation, layout, location, shapes, sizes, amounts, or other measures within acceptable variations that may occur, for example, due to manufacturing processes. The term “substantially” may be used herein to reflect this meaning. For example, items described as “substantially the same,” “substantially equal,” or “substantially planar,” may be exactly the same, equal, or planar, or may be the same, equal, or planar within acceptable variations that may occur, for example, due to manufacturing processes.

In the present disclosure, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics, and an electro-optic device, a light-emitting display device, a semiconductor circuit, and an electronic device are all included in the category of the semiconductor device.

It should be noted that, in the description of the present disclosure, above (or up) corresponds to the direction of the arrow of the direction Z, and below (or down) corresponds to the opposite direction of the arrow of the direction Z.

FIG. 1 illustrates, in a flowchart diagram form, a method 10 for fabricating a semiconductor device 1A in accordance with one embodiment of the present disclosure. FIGS. 2 to 6 illustrate, in schematic cross-sectional view diagrams, part of a flow for fabricating the semiconductor device 1A in accordance with one embodiment of the present disclosure.

With reference to FIGS. 1 to 4 , at step S11, a first substrate 111 may be provided, a first redistribution layer 131 may be formed above the first substrate 111, and a plug structure 121 may be formed on the first substrate 111.

With reference to FIG. 2 , in some embodiments, the first substrate 111 may include a bulk semiconductor substrate that is composed entirely of at least one semiconductor material, a plurality of device elements (not shown for clarity), a plurality of dielectric layers (not shown for clarity), and a plurality of conductive features (not shown for clarity). The bulk semiconductor substrate may be formed of, for example, an elementary semiconductor, such as silicon or germanium; a compound semiconductor, such as silicon germanium, silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, indium antimonide, or other III-V compound semiconductor or II-VI compound semiconductor; or combinations thereof.

In some embodiments, the first substrate 111 may further include a semiconductor-on-insulator structure which consists of, from bottom to top, a handle substrate, an insulator layer, and a topmost semiconductor material layer. The handle substrate and the topmost semiconductor material layer may be formed of the same material as the bulk semiconductor substrate aforementioned. The insulator layer may be a crystalline or non-crystalline dielectric material such as an oxide and/or nitride. For example, the insulator layer may be a dielectric oxide such as silicon oxide. For another example, the insulator layer may be a dielectric nitride such as silicon nitride or boron nitride. For yet another example, the insulator layer may include a stack of a dielectric oxide and a dielectric nitride such as a stack of, in any order, silicon oxide and silicon nitride or boron nitride. The insulator layer may have a thickness between about 10 nm and about 200 nm.

It should be noted that, in the description of present disclosure, the term “about” modifying the quantity of an ingredient, component, or reactant of the present disclosure employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or solutions. Furthermore, variation can occur from inadvertent error in measuring procedures, differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods, and the like. In one aspect, the term “about” means within 10% of the reported numerical value. In another aspect, the term “about” means within 5% of the reported numerical value. Yet, in another aspect, the term “about” means within 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value.

The plurality of device elements may be formed on the first substrate 111. Some portions of the plurality of device elements 111 may be formed in the first substrate 111. The plurality of device elements may be transistors such as complementary metal-oxide-semiconductor transistors, metal-oxide-semiconductor field-effect transistors, fin field-effect-transistors, the like, or a combination thereof.

The plurality of dielectric layers may be formed on the first substrate 111 and cover the plurality of device elements. In some embodiments, the plurality of dielectric layers may be formed of, for example, silicon oxide, borophosphosilicate glass, undoped silicate glass, fluorinated silicate glass, low-k dielectric materials, the like, or a combination thereof. The low-k dielectric materials may have a dielectric constant less than 3.0 or even less than 2.5. In some embodiments, the low-k dielectric materials may have a dielectric constant less than 2.0. The plurality of dielectric layers may be formed by deposition processes such as chemical vapor deposition, plasma-enhanced chemical vapor deposition, or the like. Planarization processes may be performed after the deposition processes to remove excess material and provide a substantially flat surface for subsequent processing steps.

The plurality of conductive features may include interconnect layers, conductive vias, and conductive pads. The interconnect layers may be separated from each other and may be horizontally disposed in the plurality of dielectric layers along the direction Z. In the present embodiment, the topmost interconnect layers may be designated as the conductive pads. The conductive vias may connect adjacent interconnect layers along the direction Z, adjacent device element and interconnect layer, and adjacent conductive pad and interconnect layer. In some embodiments, the conductive vias may improve heat dissipation and may provide structure support. In some embodiments, the plurality of conductive features may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. The plurality of conductive features may be formed during the formation of the plurality of dielectric layers.

The plurality of device elements, and the plurality of conductive features may together configure functional units. A functional unit, in the description of the present disclosure, generally refers to functionally related circuitry that has been partitioned for functional purposes into a distinct unit. In some embodiments, functional units may be typically highly complex circuits such as processor cores or accelerator units. In some other embodiments, the complexity and functionality of a functional unit may be more or less complex.

With reference to FIG. 2 , a bottom dielectric layer 115 may be formed on the first substrate 111. In some embodiments, the bottom dielectric layer 115 may be formed of, for example, silicon oxide, borophosphosilicate glass, undoped silicate glass, fluorinated silicate glass, low-k dielectric materials, the like, or a combination thereof. The bottom dielectric layer 115 may be formed by deposition processes such as chemical vapor deposition, plasma-enhanced chemical vapor deposition, or the like. Planarization processes may be performed after the deposition processes to remove excess material and provide a substantially flat surface for subsequent processing steps.

With reference to FIG. 2 , a bottom plug 123 may be formed along the bottom dielectric layer 115 and electrically coupled to the corresponding one of device elements in the first substrate 111. In other words, the bottom plug 123 may be in conjunction with the functional units in the first substrate 111. In some embodiments, the bottom plug 123 may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. In the present embodiments, the bottom plug 123 may be formed of an alloy of aluminum and copper.

With reference to FIG. 2 , a landing pad 125 may be formed on the bottom plug 123. The width W2 of the landing pad 125 may be greater than the width W1 of the bottom plug 123. In some embodiments, the landing pad 125 may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. In some embodiments, the landing pad 125 may be formed by performing a blanket deposition process with following patterning and etching processes.

With reference to FIG. 3 , a top dielectric layer 117 may be formed on the bottom dielectric layer 115 and covering the landing pad 125. The top dielectric layer 117 may be formed of the same material as the bottom dielectric layer 115, and descriptions thereof are not repeated herein. The top dielectric layer 117 may be formed by a deposition process such as chemical vapor deposition, plasma-enhanced chemical vapor deposition, or the like. A planarization process may be performed after the deposition process to remove excess material and provide a substantially flat surface for subsequent processing steps. The bottom dielectric layer 115 and the top dielectric layer 117 may together configure a first inter-dielectric layer 113.

With reference to FIG. 3 , the first redistribution layer 131 may be formed on the first inter-dielectric layer 113. In some embodiments, the first redistribution layer 131 may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. In some embodiments, the first redistribution layer 131 may be formed by performing a blanket deposition process with following patterning and etching processes. In some embodiments, the first redistribution layer 131 does not electrically couple to any functional units in the first substrate 111.

With reference to FIG. 4 , a first bottom passivation layer 141 may be formed on the first inter-dielectric layer 113 and covering the first bottom passivation layer 141. In some embodiments, the first bottom passivation layer 141 may be formed of, for example, silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, silicon carbon nitride, the like, or a combination thereof. In some embodiments, the bottom passivation layer 141 may be formed of, for example, a polymer layer including polyimide, polybenzoxazole, benzocyclobuten, epoxy, silicone, acrylates, nano-filled phenoresin, siloxane, a fluorinated polymer, polynorbornene, or the like. A planarization process may be performed until the top surface 131TS of the first redistribution layer 131 is exposed to remove excess material and provide a substantially flat surface for subsequent processing steps.

It should be noted that, in the description of the present disclosure, a surface of an element (or a feature) located at the highest vertical level along the direction Z is referred to as a top surface of the element (or the feature). A surface of an element (or a feature) located at the lowest vertical level along the direction Z is referred to as a bottom surface of the element (or the feature).

With reference to FIG. 4 , a top plug 127 may be formed along the first bottom passivation layer 141, extending to the top dielectric layer 117, and on the landing pad 125. The width W3 of the top plug 127 may be greater than the width W1 of the bottom plug 123. The width W3 of the top plug 127 may be less than the width W2 of the landing pad 125. In some embodiments, the top plug 127 may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. A patterning process with a mask layer (not shown for clarity), which masks the first redistribution layer 131, may be performed to form a plug opening (not shown for clarity) to expose a portion of the landing pad 125. A subsequent deposition process may be performed to deposit the aforementioned material to fill the plug opening. A planarization process may be performed until the top surface 131TS of the first redistribution layer 131 is exposed to remove excess material and concurrently form the top plug 127. In the present embodiment, the top plug 127 may include tungsten.

The bottom plug 123, the landing pad 125, and the top plug 127 may together configure the plug structure 121. The plug structure 121 may electrically couple to the corresponding one of device elements in the first substrate 111. In other words, the plug structure 121 may be in conjunction with the functional units in the first substrate 111.

With reference to FIGS. 1, 5, and 6 , at step S13, a first lower bonding pad 151 may be formed on the first redistribution layer 131, and a second lower bonding pad 153 may be formed on the plug structure 121 to configure a first chip 100.

With reference to FIG. 5 , a first top passivation layer 143 may be formed on the first bottom passivation layer 141. In some embodiments, the first top passivation layer 143 may be formed of a polymeric material such as polybenzoxazole, polyimide, benzocyclobutene, ajinomoto buildup film, solder resist film, or the like. The polymeric material (e.g., polyimide) may have a number of attractive characteristics such as the ability to fill openings of high aspect ratio, a relatively low dielectric constant (about 3.2), a simple depositing process, the reduction of sharp features or steps in the underlying layer, and high temperature tolerance after curing. In some embodiments, the first top passivation layer 143 may be formed by, for example, spin-coating, lamination, deposition, or the like. The deposition may include chemical vapor deposition such as plasma-enhanced chemical vapor deposition. The process temperature of the plasma-enhanced chemical vapor deposition may be between about 350° C. and about 450° C. The process pressure of the plasma-enhanced chemical vapor deposition may be between about 2.0 Torr and about 2.8 Torr. The process duration of the plasma-enhanced chemical vapor deposition may be between about 8 seconds and about 12 seconds.

With reference to FIG. 5 , in some embodiments, a plurality of pad openings 145, 147 may be formed along the first top passivation layer 143. The first redistribution layer 131 may be exposed through the pad opening 145 and the top plug 127 may be exposed through the pad opening 147. The plurality pad openings 145, 147 may be formed by a photolithography process and a subsequent etching process. In some embodiments, the etching process may be an anisotropic dry etching process using argon and tetrafluoromethane as etchants. The process temperature of the etching process may be between about 120° C. and about 160° C. The process pressure of the etching process is between about 0.3 Torr and about 0.4 Torr. The process duration of the etching process may be between about 33 seconds and about 39 seconds. Alternatively, in some embodiments, the etching process may be an anisotropic dry etching process using helium and nitrogen trifluoride as etchants. The process temperature of the etching process may be between about 80° C. and about 100° C. The process pressure of the etching process is between about 1.2 Torr and about 1.3 Torr. The process duration of the etching process may be between about 20 seconds and about 30 seconds.

With reference to FIG. 6 , a conductive material may be formed to fill the plurality pad openings 145, 147 to form the first lower bonding pad 151 and the second lower bonding pad 153, respectively and correspondingly. In some embodiments, the conductive material may be, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. In some embodiments, the plurality pad openings 145, 147 may be sequentially filled with the conductive material by sputtering or electroless plating. For example, when the plurality pad openings 145, 147 are filled by sputtering using an aluminum-copper material as source, the process temperature of sputtering may be between about 100° C. and about 400° C. The process pressure of sputtering may be between about 1 mTorr and about 100 mTorr. For another example, the plurality pad openings 145, 147 may be filled by an electroplating process using a plating solution. The plating solution may include copper sulfate, copper methane sulfonate, copper gluconate, copper sulfamate, copper nitrate, copper phosphate, or copper chloride. The pH of the plating solution may be between about 2 and about 6 or between about 3 and about 5. The process temperature of the electroplating process may be maintained between about 40° C. and about 75° C. or between about 50° C. and about 70° C.

With reference to FIG. 6 , the first lower bonding pad 151 may be formed in the pad opening 145 and may be electrically connected to the first redistribution layer 131. It should be noted that the first lower bonding pad 151 does not electrically couple to any functional units in the first substrate 111. The second lower bonding pad 153 may be formed in the pad opening 147 and may be electrically connected to the top plug 127. That is, the second lower bonding pad 153 may be in conjunction with the functional units in the first substrate 111 through the plug structure 121.

With reference to FIG. 6 , the first substrate 111, the first inter-dielectric layer 113, the plug structure 121, the first redistribution layer 131, the first bottom passivation layer 141, the first top passivation layer 143, the first lower bonding pad 151, and the second lower bonding pad 153 together configure the first chip 100. In some embodiments, the first chip 100 may be configured as a logic chip. The first chip 100 may include a front surface 100FS. It should be noted that, in the description of the present disclosure, the term “front” surface is a term of art implying the major surface of the structure upon which is formed device elements and conductive features. In the present embodiment, the front surface 100FS of the first chip 100 may be the top surface of the first top passivation layer 143.

FIG. 7 illustrates, in a schematic top-view diagram, an intermediate semiconductor device in accordance with one embodiment of the present disclosure. FIG. 8 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 7 .

With reference to FIGS. 1, 7, and 8 , at step S15, a second substrate 311 may be provided and comprising a dense region DR and a loose region LR, a plurality of storage units 321 may be formed above the second substrate 311, and a plurality of lower pads 341 may be formed above the plurality of storage units 321.

With reference to FIGS. 7 and 8 , the second substrate 311 may be provided. The second substrate 311 may include the dense region DR and a loose region LR adjacent to the dense region DR.

With reference to FIGS. 7 and 8 , in some embodiments, the second substrate 311 may be a bulk semiconductor substrate that is composed entirely of at least one semiconductor material; the bulk semiconductor substrate does not contain any dielectrics, insulating layers, or conductive features. The bulk semiconductor substrate may be formed of, for example, an elementary semiconductor, such as silicon or germanium; a compound semiconductor, such as silicon germanium, silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, indium antimonide, or other III-V compound semiconductor or II-VI compound semiconductor; or combinations thereof.

In some embodiments, the second substrate 311 may include a semiconductor-on-insulator structure which consists of, from bottom to top, a handle substrate, an insulator layer, and a topmost semiconductor material layer. The handle substrate and the topmost semiconductor material layer may be formed of the same material as the bulk semiconductor substrate aforementioned. The insulator layer may be a crystalline or non-crystalline dielectric material such as an oxide and/or nitride. For example, the insulator layer may be a dielectric oxide such as silicon oxide. For another example, the insulator layer may be a dielectric nitride such as silicon nitride or boron nitride. For yet another example, the insulator layer may include a stack of a dielectric oxide and a dielectric nitride such as a stack of, in any order, silicon oxide and silicon nitride or boron nitride. The insulator layer may have a thickness between about 10 nm and 200 nm.

A plurality of device elements (not shown for clarity) may be formed on the second substrate 311. Some portions of the plurality of device elements may be formed in the second substrate 311. The plurality of device elements may be transistors such as complementary metal-oxide-semiconductor transistors, metal-oxide-semiconductor field-effect transistors, fin field-effect-transistors, the like, or a combination thereof.

With reference to FIGS. 7 and 8 , a second bottom inter-dielectric layer 313 may be formed on the second substrate 311 and cover the plurality of device elements. In some embodiments, the second bottom inter-dielectric layer 313 may be a stacked layer structure. The second bottom inter-dielectric layer 313 may include a plurality of insulating sub-layers (not shown for clarity). Each of the plurality of insulating sub-layers may have a thickness between about micrometer and about 3.0 micrometer. The plurality of insulating sub-layers may be formed of, for example, silicon oxide, borophosphosilicate glass, undoped silicate glass, fluorinated silicate glass, low-k dielectric materials, the like, or a combination thereof. The plurality of insulating sub-layers may be formed of different materials but is not limited thereto.

A plurality of conductive features (not shown for clarity) may be formed in the second bottom inter-dielectric layer 313. The plurality of conductive features may include interconnect layers and conductive vias. The interconnect layers may be separated from each other and may be horizontally disposed in the second bottom inter-dielectric layer 313 along the direction Z. The conductive vias may connect adjacent interconnect layers along the direction Z and adjacent second device element and interconnect layer. In some embodiments, the conductive vias may improve heat dissipation and may provide structure support. In some embodiments, the plurality of conductive features may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. The plurality of conductive features may be formed during the formation of the second bottom inter-dielectric layer 313.

With reference to FIGS. 7 and 8 , the plurality of storage units 321 may be formed in the second bottom inter-dielectric layer 313. In some embodiments, the plurality of storage units 321 may be configured as a capacitor array. In some embodiments, the plurality of storage units 321 may be configured as a floating array. In some embodiments, the density of the plurality of storage units 321 above the dense region DR may be greater than the density of the plurality of storage units 321 above the loose region LR. The density of the plurality of storage units 321 may be defined as the number of the plurality of storage units 321 divided by a certain surface area containing the plurality of storage units 321. In some embodiments, the number of the storage unit 321 above the loose region LR may be zero.

With reference to FIGS. 7 and 8 , a plurality of interconnection layers 315 may be formed in the second bottom inter-dielectric layer 313. The plurality of interconnection layers 315 may be electrically coupled to the plurality of storage units 321 and the plurality of second device elements, respectively and correspondingly. In some embodiments, the plurality of interconnection layers 315 may be regarded as part of the plurality of conductive features.

With reference to FIGS. 7 and 8 , a second bottom passivation layer 331 may be formed on the second bottom inter-dielectric layer 313. In some embodiments, the second bottom passivation layer 331 may be formed of a polymeric material such as polybenzoxazole, polyimide, benzocyclobutene, ajinomoto buildup film, solder resist film, or the like. The polymeric material (e.g., polyimide) may have a number of attractive characteristics such as the ability to fill openings of high aspect ratio, a relatively low dielectric constant (about 3.2), a simple depositing process, the reduction of sharp features or steps in the underlying layer, and high temperature tolerance after curing. In some embodiments, the second bottom passivation layer 331 may be formed by, for example, spin-coating, lamination, deposition, or the like. The deposition may include chemical vapor deposition such as plasma-enhanced chemical vapor deposition. The process temperature of the plasma-enhanced chemical vapor deposition may be between about 350° C. and about 450° C. The process pressure of the plasma-enhanced chemical vapor deposition may be between about 2.0 Torr and about 2.8 Torr. The process duration of the plasma-enhanced chemical vapor deposition may be between about 8 seconds and about 12 seconds.

With reference to FIGS. 7 and 8 , the plurality of lower pads 341 may be formed on the plurality of interconnection layers 315, respectively and correspondingly. In some embodiments, pad openings (not shown in FIGS. 7 and 8 ) may be formed in the second bottom passivation layer 331 and a conductive material may be formed to fill the pad openings to form the plurality of lower pads 341. The pad openings may be formed by a photolithography process and a subsequent etching process. In some embodiments, the etching process may be an anisotropic dry etching process using argon and tetrafluoromethane as etchants. The process temperature of the etching process may be between about 120° C. and about 160° C. The process pressure of the etching process is between about 0.3 Torr and about 0.4 Torr. The process duration of the etching process may be between about 33 seconds and about 39 seconds. Alternatively, in some embodiments, the etching process may be an anisotropic dry etching process using helium and nitrogen trifluoride as etchants. The process temperature of the etching process may be between about 80° C. and about 100° C. The process pressure of the etching process is between about 1.2 Torr and about 1.3 Torr. The process duration of the etching process may be between about 20 seconds and about 30 seconds. In some embodiments, the conductive material may be, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof.

In some embodiments, the pad openings may be sequentially filled with the conductive material by sputtering or electroless plating. For example, when the pad openings are filled by sputtering using an aluminum-copper material as source, the process temperature of sputtering may be between about 100° C. and about 400° C. The process pressure of sputtering may be between about 1 mTorr and about 100 mTorr. For another example, the pad openings may be filled by an electroplating process using a plating solution. The plating solution may include copper sulfate, copper methane sulfonate, copper gluconate, copper sulfamate, copper nitrate, copper phosphate, or copper chloride. The pH of the plating solution may be between about 2 and about 6 or between about 3 and about 5. The process temperature of the electroplating process may be maintained between about 40° C. and about 75° C. or between about 50° C. and about 70° C.

FIG. 9 illustrates, in a schematic top-view diagram, an intermediate semiconductor device in accordance with one embodiment of the present disclosure. FIG. 10 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 9 .

With reference to FIGS. 1, 9, and 10 , at step S17, a plurality of first redistribution plugs 351 and a plurality of second redistribution plugs 353 may be formed on the plurality of lower pads 341, and a plurality of first supporting plugs 361 and a plurality of second supporting plugs 363 may be formed above the second substrate 311.

With reference to FIGS. 9 and 10 , a second top inter-dielectric layer 317 may be formed on the third bottom passivation layer 331. In some embodiments, the second top inter-dielectric layer 317 may be formed of, for example, silicon oxide, borophosphosilicate glass, undoped silicate glass, fluorinated silicate glass, low-k dielectric materials, the like, or a combination thereof.

With reference to FIGS. 9 and 10 , the plurality of first redistribution plugs 351, the plurality of second redistribution plugs 353, the plurality of first supporting plugs 361, and the plurality of second supporting plugs 363 may be formed in the second top inter-dielectric layer 317. For brevity, clarity, and convenience of description, only one first redistribution plug 351, one second redistribution plug 353, one first supporting plug 361, and one second supporting plug 363 are described.

With reference to FIGS. 9 and 10 , the first redistribution plug 351 may be formed on the lower pad 341 above the dense region DR. That is, the first redistribution plug 351 may be formed above the dense region DR. In some embodiments, the first redistribution plug 351 may be topographically aligned with the lower pad 341 above the dense region DR. The second redistribution plug 353 may be formed on the lower pad 341 above the loose region LR. That is, the second redistribution plug 353 may be formed above the loose region LR. In some embodiments, the second redistribution plug 353 may be topographically aligned with the lower pad 341 above the loose region LR.

With reference to FIGS. 9 and 10 , in some embodiments, the first redistribution plug 351 and the second redistribution plug 353 may be formed separately. For example, the first redistribution plug 351 may be formed by electroplating and may be formed of, for example, copper. The second redistribution plug 353 may be formed by sputtering or chemical vapor deposition and may be formed of, for example, aluminum.

In some embodiments, the width W4 of the first redistribution plug 351 may be less than the width W5 of the second redistribution plug 353. In some embodiments, the aspect ratio of the first redistribution plug 351 may be greater than the aspect ratio of the second redistribution plug 353. The aspect ratio is defined as the height of the redistribution plug divided by the width of the redistribution plug.

In some embodiments, the first supporting plug 361 and the second supporting plug 363 may be formed of, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides (e.g., tantalum carbide, titanium carbide, tantalum magnesium carbide), metal nitrides (e.g., titanium nitride), transition metal aluminides, or a combination thereof. A patterning process with a mask layer (not shown for clarity), which masks the first redistribution plug 351 and the second redistribution plug 353, may be performed to form plug openings (not shown for clarity) along the second top inter-dielectric layer 317. A subsequent deposition process may be performed to deposit the aforementioned material to fill the plug openings. A planarization process may be performed until the top surface of the second top inter-dielectric layer 317 is exposed to remove excess material and concurrently form the first supporting plug 361 and the second supporting plug 363.

In some embodiments, the distance D1 between the adjacent pair of the first redistribution plug 351 and the first supporting plug 361 above the dense region DR may be about the same as the distance D2 between the adjacent pair of the first supporting plug 361 above the dense region DR and the second supporting plug 363 above the dense region DR. In some embodiments, the distance D1 between the adjacent pair of the first redistribution plug 351 and the first supporting plug 361 above the dense region DR may be different from the distance D2 between the adjacent pair of the first supporting plug 361 above the dense region DR and the second supporting plug 363 above the dense region DR.

In some embodiments, the distance D3 between the adjacent pair of the second redistribution plug 353 and the first supporting plug 361 above the loose region LR may be about the same as the distance D4 between the adjacent pair of the first supporting plug 361 above the loose region LR and the second supporting plug 363 above the loose region LR. In some embodiments, the distance D3 between the adjacent pair of the second redistribution plug 353 and the first supporting plug 361 above the loose region LR may be different from the distance D4 between the adjacent pair of the first supporting plug 361 above the loose region LR and the second supporting plug 363 above the loose region LR.

In some embodiments, the distance D1 between the adjacent pair of the first redistribution plug 351 and the first supporting plug 361 above the dense region DR may be about the same as the distance D3 between the adjacent pair of the second redistribution plug 353 and the first supporting plug 361 above the loose region LR. In some embodiments, the distance D1 between the adjacent pair of the first redistribution plug 351 and the first supporting plug 361 above the dense region DR may be different from the distance D3 between the adjacent pair of the second redistribution plug 353 and the first supporting plug 361 above the loose region LR.

FIG. 11 illustrates, in a schematic top-view diagram, an intermediate semiconductor device in accordance with one embodiment of the present disclosure. FIG. 12 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 11 .

With reference to FIGS. 1, 11, and 12 , at step S19, a plurality of second redistribution layers 355 may be formed on the plurality of first redistribution plugs 351, the plurality of second redistribution plugs 353, the plurality of first supporting plugs 361, and the plurality of second supporting plugs 363.

With reference to FIGS. 11 and 12 , the plurality of second redistribution layers 355 may be formed on the second top inter-dielectric layer 317. For brevity, clarity, and convenience of description, only one second redistribution layer 355 above the dense region DR and one second redistribution layer 355 above the loose region LR are described. The second redistribution layer 355 above the dense region DR may be formed on the first redistribution plug 351, the first supporting plug 361 above the dense region DR, and the second supporting plug 363 above the dense region DR. The first supporting plug 361 above the dense region DR and the second supporting plug 363 above the dense region DR may be floating.

The second redistribution layer 355 above the loose region LR may be formed on the second redistribution plug 353, the first supporting plug 361 above the loose region LR, and the second supporting plug 363 above the loose region LR. The first supporting plug 361 above the loose region LR and the second supporting plug 363 above the loose region LR may be floating.

The first supporting plug 361 and the second supporting plug 363 may provide additional support during the following bonding process as will be illustrated later. The second redistribution layer 355 may be formed with a procedure similar to the first redistribution layer 131, and descriptions thereof are not repeated herein.

FIG. 13 illustrates, in a schematic top-view diagram, an intermediate semiconductor device illustrated in accordance with one embodiment of the present disclosure. FIG. 14 is a schematic cross-sectional view diagram taken along a line A-A′ in FIG. 13 .

With reference to FIGS. 11, 13, and 14 , at step S21, a plurality of upper pads 343 may be formed on the plurality of second redistribution layers 355 to configure a second chip 300.

With reference to FIGS. 13 and 14 , a second top passivation layer 333 may be formed on the second top inter-dielectric layer 317 to cover the plurality of second redistribution layers 355. The plurality of upper pads 343 may be formed on the plurality of second redistribution layers 355, respectively and correspondingly. In some embodiments, the plurality of upper pads 343 may be formed above the plurality of second supporting plugs 363, respectively and correspondingly.

The second substrate 311, the second bottom inter-dielectric layer 313, the plurality of interconnection layers 315, the second top inter-dielectric layer 317, the plurality of storage units 321, the second bottom passivation layer 331, the plurality of lower pads 341, the plurality of first redistribution plugs 351, the plurality of second redistribution plugs 353, the plurality of first supporting plugs 361, the plurality of second supporting plugs 363, the plurality of second redistribution layers 355, the second top passivation layer 333, and the plurality of upper pads 343 together configure the second chip 300. The second chip 300 may include a front surface 300F S. In the present embodiment, the front surface 300F S of the second chip 300 may be the top surface of the second top passivation layer 333.

In some embodiments, the third chip 300 may be configured as a memory chip. The plurality of upper pads 343 may be configured as input/output of the second chip 300. The plurality of first redistribution plugs 351, the plurality of second redistribution plugs 353, and the plurality of second redistribution layers 355 may in conjunction with the plurality of upper pads 343 to transmit signal of the plurality of storage units 321 to the plurality of upper pads 343.

FIG. 15 illustrates, in a schematic cross-sectional view diagram, part of the flow for fabricating the semiconductor device 1A in accordance with one embodiment of the present disclosure.

With reference to FIGS. 1 and 15 , at step S23, the second chip 300 may be bonded onto the first chip 100 to form the semiconductor device 1A.

With reference to FIG. 15 , the second chip 300 may be bonded onto the first chip 100 in a face-to-face configuration through a hybrid bonding process. The front surface 300F S of the second chip 300 may be bonded onto the front surface 100F S of the first chip 100. After the hybrid bonding process, the second chip 300 (configured as the memory chip) and the first chip 100 (configured as the logic chip) may together configure an integrated circuit package. For example, the upper pad 343 at the dense region DR may be disposed on the second lower bonding pad 153. The upper pad 343 at the loose region LR may be disposed on the first lower bonding pad 151.

In some embodiments, the hybrid bonding process may be, for example, thermo-compression bonding, passivation-capping-layer assisted bonding, or surface activated bonding. For example, the hybrid bonding process may include activating exposed surfaces of the second top passivation layer 333 of the second chip 300 and the first top passivation layer 143 (e.g., in a plasma process), cleaning the second top passivation layer 333 and the first top passivation layer 143 after activation, contacting the activated surface of the second top passivation layer 333 and the activated surface of the first top passivation layer 143, and performing a thermal annealing process to strengthen the bonding between the second top passivation layer 333 and the first top passivation layer 143.

In some embodiments, the process pressure of the hybrid bonding process may be between about 100 MPa and about 150 MPa. In some embodiments, the process temperature of the hybrid bonding process may be between about room temperature (e.g., 25° C.) and about 400° C. In some embodiments, surface treatments such as wet chemical cleaning and gas/vapor-phase thermal treatments may be used to lower the process temperature of the hybrid bonding process or to shorten the time consuming of the hybrid bonding process.

In some embodiments, the hybrid bonding process may include dielectric-to-dielectric bonding, metal-to-metal bonding, and metal-to-dielectric bonding. The dielectric-to-dielectric bonding may originate from the bonding between the second top passivation layer 333 and the first top passivation layer 143. The metal-to-metal bonding may originate from the bonding between the first lower bonding pad 151 and the upper pad 343, and between the second lower bonding pad 153 and the upper pad 343. The metal-to-dielectric bonding may originate from the bonding between the first top passivation layer 143 and the plurality of upper pads 343 and between the second top passivation layer 333 and the first lower bonding pad 151 and/or the second lower bonding pad 153.

In some embodiments, when the first top passivation layer 143 and the second top passivation layer 333 are formed of, for example, silicon oxide or silicon nitride, the bonding between the first top passivation layer 143 and the second top passivation layer 333 may be based on the hydrophilic bonding mechanism. Hydrophilic surface modifications may be applied to the first top passivation layer 143 and the second top passivation layer 333 before bonding.

In some embodiments, when the first top passivation layer 143 and the second top passivation layer 333 are formed of polymer adhesives such as polyimide, benzocyclobutenes, and polybenzoxazole, the bonding between the first top passivation layer 143 and the second top passivation layer 333 may be based on thermo-compression bonding.

In some embodiments, a thermal annealing process may be performed after the bonding process to enhance dielectric-to-dielectric bonding and to induce thermal expansion of metal-to-metal bonding so as to further improve the bonding quality.

The first redistribution plug 351 and the second redistribution plug 353 having different aspect ratios and/or material may be used to fine tune resistances for different redistribution paths. As a result, the performance of the semiconductor device 1A may be improved.

FIGS. 16 to 21 illustrate, in schematic cross-sectional view diagrams, semiconductor devices 1B, 1C, 1D, 1E, 1F, and 1G in accordance with some embodiments of the present disclosure.

With reference to FIG. 16 , the semiconductor device 1B may have a structure similar to that illustrated in FIG. 15 . The same or similar elements in FIG. 16 as in FIG. 15 have been marked with similar reference numbers and duplicative descriptions have been omitted.

With reference to FIG. 16 , the upper pad 343 at the loose region LR may be disposed on the second lower bonding pad 153. That is, the upper pad 343 at the loose region LR may be in conjunction with the functional units of the first chip 100 through the plug structure 121. Signal such as control signal may be transmitted from the first chip 100 to the plurality of storage units 321 through the plug structure 121, the second lower bonding pad 153, and the upper pad 343 at the at the loose region LR. The upper pad 343 at the dense region DR may be disposed on the first lower bonding pad 151. Signal such as data signal may be transmitted from the plurality of storage units 221 through the upper pad 343 at the dense region DR, the first lower bonding pad 151, and the first redistribution layer 131 to an external reading unit without passing through the conductive features, the plug structure 121, and functional units of the first chip 100.

With reference to FIG. 17 , the semiconductor device 1C may have a structure similar to that illustrated in FIG. 15 . The same or similar elements in FIG. 17 as in FIG. 15 have been marked with similar reference numbers and duplicative descriptions have been omitted.

With reference to FIG. 17 , the semiconductor device 1C may include a first barrier layer 161 disposed between the first top passivation layer 143 and the second lower bonding pad 153, between the top plug 127 and the second lower bonding pad 153, and between the second lower bonding pad 153 and the first bottom passivation layer 141. The first barrier layer 161 may be formed of, for example, titanium, titanium nitride, or a combination thereof. The first barrier layer 161 may be formed by, for example, atomic layer deposition, physical vapor deposition, chemical vapor deposition, or other applicable deposition process.

With reference to FIG. 18 , the semiconductor device 1D may have a structure similar to that illustrated in FIG. 15 . The same or similar elements in FIG. 18 as in FIG. 15 have been marked with similar reference numbers and duplicative descriptions have been omitted.

With reference to FIG. 18 , the semiconductor device 1D may include a second barrier layer 163 disposed between the first bottom passivation layer 141 and the top plug 127, between the top dielectric layer 117 and the top plug 127, and between the landing pad 125 and the top plug 127. The second barrier layer 163 may be formed of, for example, titanium, titanium nitride, or a combination thereof. The second barrier layer 163 may be formed by, for example, atomic layer deposition, physical vapor deposition, chemical vapor deposition, or other applicable deposition process.

With reference to FIG. 19 , the semiconductor device 1E may have a structure similar to that illustrated in FIG. 15 . The same or similar elements in FIG. 19 as in FIG. 15 have been marked with similar reference numbers and duplicative descriptions have been omitted.

With reference to FIG. 19 , in the semiconductor device 1E, a second barrier layer 163 may be disposed between the first bottom passivation layer 141 and the top plug 127, between the top dielectric layer 117 and the top plug 127, and between the landing pad 125 and the top plug 127. In some embodiments, the second barrier layer 163 may have a U-shaped cross-sectional profile extending toward the landing pad 125. The top surface of the second barrier layer 163 and the top surface of the top plug 127 may be recessed to a vertical level VL1 between the top surface 131TS and the bottom surface 131BS of the first redistribution layer 131.

With reference to FIG. 19 , a third barrier layer 165 may be conformally disposed between the second lower bonding pad 153 and the top plug 127. In some embodiments, the third barrier layer 165 may further include a U-shaped protrusion 165-1 extending toward the top plug 127 and disposed on the top surface of the top plug 127. In other words, the bottom surface 165BS of the U-shaped protrusion 165-1 (i.e., the bottom surface of the third barrier layer 165) may be lower than the top surface 131TS of the first redistribution layer 131 and higher than the bottom surface 131BS of the first redistribution layer 131. Accordingly, the second lower bonding pad 153 may further include a protrusion portion 155 extending toward the top plug 127 and disposed in the recess configured by the U-shaped protrusion 165-1. In some embodiments, the bottom surface 165BS of the U-shaped protrusion 165-1 may be rounding. In some embodiments, the bottom surface 165BS of the U-shaped protrusion 165-1 may be substantially flat.

With reference to FIG. 19 , a fourth barrier layer 167 may be conformally disposed between the first lower bonding pad 151 and the first redistribution layer 131. The third barrier layer 165 and the fourth barrier layer 167 may be formed of the same material as the first barrier layer 161, and descriptions thereof are not repeated herein.

With reference to FIG. 20 , the semiconductor device 1F may have a structure similar to that illustrated in FIG. 15 . The same or similar elements in FIG. 20 as in FIG. 15 have been marked with similar reference numbers and duplicative descriptions have been omitted.

With reference to FIG. 20 , a molding layer 611 may be formed on the first chip 100 to cover the second chip 300. In some embodiments, the molding layer 611 may be formed of a molding compound such as polybenzoxazole, polyimide, benzocyclobutene, epoxy laminate, or ammonium bifluoride. The molding layer 611 may be formed by compressive molding, transfer molding, liquid encapsulant molding, and the like. For example, a molding compound may be dispensed in liquid form. Subsequently, a curing process is performed to solidify the molding compound. The formation of molding compound may overflow the first chip 100 so that molding compound may completely cover the second chip 300. The first chip 100, the second chip 300, and the molding layer 611 together configure the semiconductor device 1F.

With reference to FIG. 21 , the semiconductor device 1G may have a structure similar to that illustrated in FIG. 15 . The same or similar elements in FIG. 21 as in FIG. 15 have been marked with similar reference numbers and duplicative descriptions have been omitted.

With reference to FIG. 21 , the first chip 100 may include an additional set of plug structure 121, first redistribution layer 131, first lower bonding pad 151, and second lower bonding pad 153 as shown on the left side of the first chip 100. The second chip 300 may be disposed on the first chip 100 in the same manner as illustrated in FIG. and descriptions thereof are not repeated herein.

With reference to FIG. 21 , a third chip 500 may be provided with a procedure similar to the second chip 300 as illustrated in FIGS. 7 to 14 , and descriptions thereof are not repeated herein. The third chip 500 may be bonded onto the left side of the first chip 100 with a procedure similar to that illustrated in FIG. 15 , and descriptions thereof are not repeated herein.

One aspect of the present disclosure provides a semiconductor device including a first chip including a first substrate, a first redistribution layer positioned above the first substrate, a first lower bonding pad positioned on the first redistribution layer, and a second lower bonding pad positioned above the first substrate and distant from the first lower bonding pad; and a second chip including a dense region and a loose region adjacent to the dense region, a plurality of upper pads positioned on the first lower bonding pad and the second lower bonding pad, a plurality of second redistribution layers positioned on the plurality of upper pads, and a first redistribution plug and a second redistribution plug respectively and correspondingly positioned on the plurality of second redistribution layers. The first redistribution plug is at the dense region and includes a first aspect ratio. The second redistribution plug is at the loose region and includes a second aspect ratio less than the first aspect ratio.

Another aspect of the present disclosure provides a semiconductor device including a first chip including a first substrate, a first redistribution layer positioned above the first substrate, a first lower bonding pad positioned on the first redistribution layer, a second lower bonding pad positioned above the first substrate and distant from the first lower bonding pad, and a plug structure positioned between the second lower bonding pad and the first substrate; and a second chip including a dense region and a loose region adjacent to the dense region, a plurality of upper pads positioned on the first lower bonding pad and the second lower bonding pad, a plurality of second redistribution layers positioned on the plurality of upper pads, and a first redistribution plug and a second redistribution plug respectively and correspondingly positioned on the plurality of second redistribution layers. The first redistribution plug is at the dense region, electrically couples to the first redistribution layer, and includes a first aspect ratio. The second redistribution plug is at the loose region, electrically couples to the plug structure, and includes a second aspect ratio less than the first aspect ratio.

Another aspect of the present disclosure provides a method for fabricating a semiconductor device including providing a first chip including a first substrate, a first redistribution layer above the first substrate, a first lower bonding pad on the first redistribution layer, and a second lower bonding pad above the first substrate and distant from the first lower bonding pad; providing a second chip including a second substrate including a dense region and a loose region adjacent to the dense region, a plurality of storage units above the second substrate, a first redistribution plug above the dense region and a second redistribution plug above the loose region, a plurality of second redistribution layers on the first redistribution plug and the second redistribution plug, respectively and correspondingly, a plurality of upper pads on the plurality of second redistribution layers, respectively and correspondingly; and bonding the second chip onto the first chip in a face-to-face manner to contact the plurality of upper pads to the first lower bonding pad and the second lower bonding pad. The first redistribution plug includes a first aspect ratio, and the second redistribution plug includes a second aspect ratio less than the first aspect ratio.

Due to the design of the semiconductor device of the present disclosure, the first redistribution plug 351 and the second redistribution plug 353 having different aspect ratios may be used to fine tune resistances for different redistribution paths. As a result, the performance of the semiconductor device 1A may be improved. In addition, data signals may be transmitted through the upper pads 343, the first lower bonding pad 151, and the first redistribution layer 131 without passing through the conductive features, the plug structure 121, and functional units of the first chip 100. As a result, the distance of transmittance may be reduced so that the performance of the semiconductor device 1A may be improved. Furthermore, the power consumption of the semiconductor device 1A may be reduced due to the shorter distance of transmittance.

Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, and steps. 

What is claimed is:
 1. A method for fabricating a semiconductor device, comprising: providing a first chip comprising a first substrate, a first redistribution layer positioned above the first substrate, a first lower bonding pad positioned on the first redistribution layer, and a second lower bonding pad positioned above the first substrate and distant from the first lower bonding pad; and providing a second chip comprising: a dense region and a loose region adjacent to the dense region; a plurality of upper pads positioned on the first lower bonding pad and the second lower bonding pad; a plurality of second redistribution layers positioned on the plurality of upper pads; and a first redistribution plug and a second redistribution plug respectively and correspondingly positioned on the plurality of second redistribution layers; bonding the second chip onto the first chip in a face-to-face manner to contact the plurality of upper pads to the first lower bonding pad and the second lower bonding pad; wherein the first redistribution plug is at the dense region and comprises a first aspect ratio; wherein the second redistribution plug is at the loose region and comprises a second aspect ratio less than the first aspect ratio.
 2. The method of claim 1, further comprising: forming a plurality of lower pads on the first redistribution plug and the second redistribution plug; and forming a plug structure between the second lower bonding pad and the first substrate, wherein the plug structure is electrically coupled to the first redistribution plug.
 3. The method of claim 2, wherein forming the plug structure comprises forming a bottom plug on the first substrate, forming a landing pad on the bottom plug, and forming a top plug between the landing pad and the second lower bonding pad.
 4. The method of claim 3, wherein the bottom plug comprises aluminum, copper, or a combination thereof, and the top plug comprises tungsten.
 5. The method of claim 4, wherein the second chip comprises a plurality of storage units above the first chip and electrically coupled to the first lower bonding pad or the second lower bonding pad, the plurality of storage units are configured as a capacitor array or a floating array, and the first chip is configured as a logic chip and the second chip is configured as a memory chip.
 6. The method of claim 5, further comprising: forming a plurality of first supporting plugs respectively and correspondingly on the plurality of second redistribution layers, wherein the plurality of first supporting plugs are at the dense region and the loose region, respectively and correspondingly; and forming a plurality of second supporting plugs respectively and correspondingly on the plurality of second redistribution layers, wherein the plurality of second supporting plugs are at the dense region and the loose region, respectively and correspondingly.
 7. The method of claim 6, wherein a distance between an adjacent pair of the first redistribution plug and the first supporting plug at the dense region and a distance between an adjacent pair of the first supporting plug and the second supporting plug at the dense region are substantially the same.
 8. The method of claim 6, wherein a distance between an adjacent pair of the first redistribution plug and the first supporting plug at the dense region and a distance between an adjacent pair of the first supporting plug and the second supporting plug at the dense region are different.
 9. The method of claim 6, wherein a distance between an adjacent pair of the second redistribution plug and the first supporting plug at the loose region and a distance between an adjacent pair of the first supporting plug and the second supporting plug at the loose region are substantially the same.
 10. The method of claim 6, wherein a distance between an adjacent pair of the second redistribution plug and the first supporting plug at the loose region and a distance between an adjacent pair of the first supporting plug and the second supporting plug at the loose region are different.
 11. The method of claim 6, wherein a distance between an adjacent pair of the first redistribution plug and the first supporting plug at the dense region and a distance between an adjacent pair of the second redistribution plug and the first supporting plug at the loose region are substantially the same.
 12. The method of claim 6, wherein a distance between an adjacent pair of the first redistribution plug and the first supporting plug at the dense region and a distance between an adjacent pair of the second redistribution plug and the first supporting plug at the loose region are different.
 13. The method of claim 6, wherein the plurality of first supporting plugs and the plurality of second supporting plugs are floating.
 14. A method for fabricating a semiconductor device, comprising: providing a first chip comprising a first substrate, a first redistribution layer above the first substrate, a first lower bonding pad on the first redistribution layer, a second lower bonding pad above the first substrate and distant from the first lower bonding pad, and a plug structure between the second lower bonding pad and the first substrate; and providing a second chip comprising: a dense region and a loose region adjacent to the dense region; a plurality of upper pads on the first lower bonding pad and the second lower bonding pad; a plurality of second redistribution layers on the plurality of upper pads; and a first redistribution plug and a second redistribution plug respectively and correspondingly on the plurality of second redistribution layers; bonding the second chip onto the first chip in a face-to-face manner to contact the plurality of bonding the second chip onto the first chip in a face-to-face manner to contact the plurality of upper pads to the first lower bonding pad and the second lower bonding pad; s to the first lower bonding pad and the second lower bonding pad; wherein the first redistribution plug is at the dense region, electrically couples to the first redistribution layer, and comprises a first aspect ratio; wherein the second redistribution plug is at the loose region, electrically couples to the plug structure, and comprises a second aspect ratio less than the first aspect ratio.
 15. The method of claim 14, further comprising: forming a plurality of lower pads on the first redistribution plug and the second redistribution plug, wherein the plug structure comprises a bottom plug on the first substrate, a landing pad on the bottom plug, and a top plug between the landing pad and the second lower bonding pad.
 16. The method of claim 15, wherein the bottom plug comprises aluminum, copper, or a combination thereof, and the top plug comprises tungsten.
 17. The method of claim 16, wherein the second chip comprises a plurality of storage units above the first chip and electrically coupled to the first lower bonding pad or the second lower bonding pad.
 18. The method of claim 17, wherein the plurality of storage units are configured as a capacitor array or a floating array.
 19. The method of claim 18, wherein the first chip is configured as a logic chip and the second chip is configured as a memory chip.
 20. The method of claim 19, further comprising: forming a plurality of first supporting plugs respectively and correspondingly on the plurality of second redistribution layers, wherein the plurality of first supporting plugs are at the dense region and the loose region, respectively and correspondingly; and forming a plurality of second supporting plugs respectively and correspondingly on the plurality of second redistribution layers, wherein the plurality of second supporting plugs are at the dense region and the loose region, respectively and correspondingly; wherein the plurality of first supporting plugs and the plurality of second supporting plugs are floating. 